This invention pertains to data storage disk files and more particularly to a structure and method for the precision alignment of transducer heads with respect to each other and the storage media surface.
A magnetic disk file is initialized by servowriting the surfaces of the disks to provide permanent data relating to the tracks, sector identification and servo data for seek and track follow. These functions are performed during the build process by a servowriter that must function with a high precision of head orientation, disk angular position and disk speed. Using a two disk sector servo file as an example, the servowriting device has a pair of speed heads with a precise angular separation on a common track to determine the rotational speed as a signal is sequentially sent by one head and received by the other. A clock head receives signals from a clock track that it precisely written to divide the disk into precision angular increments. Finally, four aligned servo write heads in two opposing pairs confront the disk surfaces and are used to write the permanent data consecutively track by track across all the disk surfaces.
To enable maximum areal densities, it is important that the servowriting be done with the greatest precision that the state of the art will allow. This requires precise alignment of the transducer heads and frequent inspection and readjustment of head position to assure that exacting dimensional specifications are maintained.
This has commonly been accomplished using a master servowriter to create standard files that are used to certify production servowriters each day to assure proper gap alignment. This method has limitations in providing only an indirect sensing of head gap alignment and the obvious possibility that damage or maladjustment may occur with respect to the master servowriter or the standard files. It has been possible to align heads with respect to the surface of a glass disk or plate by viewing from the opposite side with respect to a grid found upon the glass surface which confronts the transducer gap. This approach is shown in U.S. Pat. No. 3,681,489. In actual practice many critical transducer gap locations are not accessible from the opposite surface and servo write heads which are aligned to write opposite surfaces on a common disk are never so accessible.